Output maximization of a 7.25 GHz ECR ion source

摘要

The operating parameters of the Rossendorf 7.25 GHz ECR ion source have been investigated in respect to maximize the current output for different ions, especially for the high charge states. The main features of the ion source and the experimental setup are the following: - single stage, floating disk supported discharge with UHF input power <200 W; - air cooled plasma chamber of 83 mm diameter and 310 mm length; - solenoid coil packages generating a mirror ratio of 2; - Fe-Nd-B multipole (hexapole), creating the magnetic resonance flux density at a radius of about 35 mm; - single gap ion acceleration; - magnetic, double focusing q/A beam analyzator with an acceptance of about (pi)*160 mm mrad; beam probe and Faraday cup. Gas pressure and gas composition, axial magnetic field and UHF power have been varied to maximize the ion output. In comparison to single stage devices with similar UHF frequency the ion output of our machine is moderate and amounts to e.g. 8 (mu)A for Ar(sup 9+) or 1.5 (mu)A for Xe(sup 18+). Basic parameters and limits of the source have been determined and the result of the optimization process is reproducible. (orig.)